You can middle click a link to open the link in a new tab.
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You can use the Menu Editor extension to swap the two context menu entries.
*Menu Editor: https://addons.mozilla.org/firefox/addon/710
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You can also do this with code in userChrome.css<br />
See:
* http://kb.mozillazine.org/Editing_configuration
Add this code to [http://kb.mozillazine.org/UserChrome.css userChrome.css] below the @namespace line.
<pre><nowiki>@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */
#contentAreaContextMenu > * { -moz-box-ordinal-group: 2; }
#context-openlink { -moz-box-ordinal-group: 1 !important; }
</nowiki></pre>